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HOMESERVICE MANUALSCHEVROLET2001CHEVY EXPRESS G2500, VAN CARGO EXTENDED, 5.7 R, L31/KL8REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 359 (DATA LINK COMMUNICATION SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC U1000 AND U1255: OPERATING PARAMETER ASSOCIATIONTEST DESCRIPTION
2001 Chevrolet Chevy Express G2500, Van Cargo Extended, 5.7 R, L31/KL8

Test Description

2001 Chevrolet Chevy Express G2500, Van Cargo Extended, 5.7 R, L31/KL8SECTION Test Description
WARNING: This page is about a different car, the 2002 Buick Regal and 2002 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

  1. 1.  A Lost Communication with XXX DTC with a history status may indicate the cause of U1000.
  2. 2.  The modules that is not communicating is the likely cause of U1000 or U1255 being set.

    The following modules communicate on the class 2 serial data circuit:

    • PCM
    • EBCM
    • SDM
    • IPC
    • BCM
    • HVAC Control Module
    • VIU
  3. 5.  The module which was not communicating may have set Lost Communication with XXX DTCs for those modules that it was monitoring.
  4. 6.  The module which was not communicating may have set Lost Communication with XXX DTCs for those modules that it was monitoring.
  5. 7.  The module that was not communicating may have set Lost Communication with XXX DTCs for those modules that the module was monitoring.
  6. 11.  The modules that communicate indicate the module that cannot communicate. You must clear the DTC from the modules in order to avoid future misdiagnosis.
  7. 13.  If all modules are communicating, the module that set U1000 may have done so due to some other condition.
  8. 14.  The module that set U1000 is the likely cause of the malfunction.
Fig 1: Identifying DTC U1000 and U1255 Diagnostic Table (1 Of 2)
G01754703Courtesy of GENERAL MOTORS CORP.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.